Process for depicting objects using an image reproduction device

ABSTRACT

PCT No. PCT/DE95/01854 Sec. 371 Date Jun. 20, 1997 Sec. 102(e) Date Jun. 20, 1997 PCT Filed Dec. 21, 1995 PCT Pub. No. WO96/20469 PCT Pub. Date Jul. 4, 1996In a process for depicting objects using an image reproduction device, data that describe the form and position of objects are fed into at least one image memory. The data are read out line by line and, along with other data describing the other properties of the objects, processed to form video signals which are fed to the image reproduction device.

This invention relates to a procedure for displaying objects using animage reproduction device.

Image reproduction devices are increasingly being used for displayinginformation which exists in the form of data and which is made visibleas two-dimensional objects using the resources of what is termedcomputer graphics. Thus display devices for aircraft have become known,for example, in which various symbols are displayed on a screen andindicate the most important information to the pilot in a clear manner.A display of this type is described in U.S. Pat. No. 5,420,582, forexample.

In the known procedures for the display of two-dimensional objects usingan image reproduction device, the contour of an object is firstcalculated in each case. Thereafter, all the image elements which aresituated inside the calculated contour are written to an image memorywith the requisite information for the respective color of the object.In order to obtain the signals required for the image reproductiondevice (video signals), the image memory is then read line by line.Depending on the desired local resolution and the resolution in theplane of colour, image memories of considerable capacity are necessaryfor such procedures. Moreover, a relatively large amount of data has tobe processed when writing to and reading from memory, which eithernecessitates very fast circuits or results in a restriction of thedisplay of rapidly moving objects.

Particularly when displaying information by means of objects which aresituated in different planes and which may be both two-dimensional orlinear, considerable computational effort is necessary for preparing thegraphic data before writing them to the image memories. Thus, forexample, all the objects involved have to be recalculated if an objectmoves over the boundaries of one or more other objects. For thispurpose, a computational capacity has to be made available which ishigher the more rapidly the modifications are to be made.

The object of the present invention is to provide a procedure fordisplaying objects using an image reproduction device in which amultiplicity of displays which is as large as possible and a high rateof modification can be achieved with a given computer output.

This object is achieved according to the invention in that data whichdescribe the shape and position of the objects are fed in and are storedin at least one image memory, that the data are read out line by lineand are processed with further data which are fed in and which describefurther properties of the objects to form video signals which are fed tothe image reproduction device.

Processing to form image signals is preferably effected in that thefurther data which describe further properties of the objects arewritten to at least one further memory, that the data which describe theshape and position and which are read out are fed as addresses to the atleast one further memory, and that the further data are read out asdigital video signals under the addresses from the at least one furthermemory.

By means of the procedure according to the invention, a plurality ofobjects can be moved rapidly and independently of each other on thescreen of the image reproduction device, without a completerecalculation of the image being necessary in each phase of movement.For example, in order to produce an artificial horizon on a screen, amultiplicity of scales and markings are necessary on the screen inaddition to the blue area of the sky and the mainly brown area of theearth. In this respect, for example, the brown area of the earthrepresents an object which is situated inside the oval visible region infront of the blue area of the sky. If it is only the artificial horizonwhich alters, due to a rolling or pitching movement of the aircraft forexample, a graphic processor connected upstream merely has torecalculate the new form or position of the "brown area" object. All theother data which possibly influence the display of this object can beleft unchanged.

The procedure according to the invention also has the advantage that therequisite storage capacity is significantly reduced compared with thestorage of the complete image of the object. In a conventional storageprocedure it is necessary to store an amount of informationcorresponding to the colour resolution for each image element of theobject. In the procedure according to the invention this amount ofinformation is only stored once.

A development of the procedure according to the invention consists ofmixing the digital video signals with further digital video signalswhich are fed in. A background can thereby be placed underneath thedisplay of objects produced by the procedure according to the invention.This background may be a map, for example, and the objects to bedisplayed may be flight information, such as radio beacons, aircorridors, aircraft symbols and alphanumeric data. The further digitalvideo signals which are fed in may also be generated using a furtherdevice according to the procedure according to the invention. Thus it ispossible, for example, to generate symbols, scales and pointers with afirst device and to place these underneath an image of a landscapeprovided with a second device, or to cascade a plurality ofimage-producing units in order to superimpose different types ofsymbols.

Another development of the procedure according to the invention consistsof storing data which describe the shape and position of line objects ina first image memory and storing data which describe the shape andposition of two-dimensional objects in a second image memory, whereinthe data read out from the image memories are fed as addresses to afirst and a second further memory in each case. A different treatment oftwo-dimensional and line objects which is matched to the respectiverequirements is thus possible.

Although the further properties may be any properties of the objects,provision is preferably made in the procedure according to the inventionfor the further properties of the objects to be the colour andtransparency thereof. Further attributes may be flashing displays,hatching for two-dimensional objects and broken lines for line objects,for example.

In another development of the procedure according to the invention, thedata which describe the shape and position comprise a plurality of bitpositions for each image element and each bit position is assigned to adisplay plane, particularly to an object to be displayed in this displayplane. In this respect, the further data for each address can preferablybe fed in independently and can be stored in the further memories.

With this further development, any colours can be assigned to theindividual objects and to those areas on which the objects overlap.These colours can also be changed during the display, for example imageby image. This can be effected with the procedure according to theinvention without the graphic processor having to recalculate the objectas such--namely its shape and position.

A separate treatment of line and two-dimensional objects has proved tobe particularly advantageous in the procedure according to theinvention, in that digital video signals which represent the colour ofthe line objects and digital video signals which represent the colour oftwo-dimensional objects are each mixed with a background signal using atransparency factor, and that the mixed products are mixed with eachother using a further factor which describes the line intensity. In thisrespect, the factor which describes the line intensity preferably fallsoff gradually from the middles of the lines to their edges in order toavoid foldover distortions.

For the mixed display of line and two-dimensional objects in a pluralityof planes, it is necessary to adapt the lines, as regards their colourand priority, to the other objects. It is thus necessary, for example,to interrupt a line if it is situated in part behind a non-transparenttwo-dimensional object. Adaptations of this type can advantageously beachieved with the procedure according to the invention in that the datawhich describe the shape and position comprise a plurality of bitpositions for each image element, that a bit position is assigned toeach display plane, particularly to an object to be displayed in thisdisplay plane, that signals which can be taken from the first furthermemory and which indicate the plane of the respective line object arecompared with the data read out from the second image memory, and thatthe digital video signals representing the lines are replaced by digitalvideo signals which represent objects for those image elements for whichthe comparison shows that a line runs behind an object.

In order to store the data which describe the shape and the position ofeach object, an image memory can be used which is known in the art andwhich only comprises 1 bit per image element. According to anotherdevelopment, it is possible to reduce this storage requirement by

deriving coordinates of the image elements which form the contour fromthe data fed in which each describe the shape and position of an object,

writing the coordinates to a first memory,

feeding in the further data fed in, which describe further properties ofthe respective object, and storing these data in a second memory,

reading out the content of the first memory line by line,

for the first image element forming the contour within each line,setting a signal which is to be fed to the image reproduction device toa value formed by the data read out from the second memory, and

for a second image element forming the contour within the same line ineach case, resetting the signal which is to be fed to the imagereproduction device.

According to an advantageous form of this development, in order toachieve unambiguity when reading out the coordinates of the contours andduring the processing with the data which determine the colour, thecoordinates are derived in such a way that the number of image elementsforming the contour of each object is even within each line.

In order to ensure this even-numbered quality for any shapes of objects,provision can be made according to this development for sections of thecontour which do not run in the direction of the lines to be formed fromimage elements at their end points and from one image element for eachcut line, for sections of the contour which run in the direction of thelines to be formed from image elements at those ends which are situatedat external corners of the object, and for individual image elementswhich are situated at the point of intersection of two sections of thecontour which do not run in the direction of the lines and which form acorner of the object not to be written to the memory.

According to another advantageous form of this development, for thesuccessive derivation of the coordinates, the fed-in data which containthe contour are fed in, the (X, Y) coordinates are temporarily storedfor three successive timing cycles, two successive coordinates and twocoordinates which are delayed by two timing cycles in relation to eachother are compared in each case, and instructions for the modification,non-modification or setting of coordinates previously stored in thefirst memory are produced by a logical linkage of the comparisonresults.

If the graphic generator which supplies the data fed in is appropriatelydesigned, it already generates the coordinates in the grid which ispredetermined by address space of the image memory. However, it may bequite useful to employ a commercially available graphic generator, theresolution of which is higher than the resolution provided by the imagememory and the image reproduction device, for example so that thecoordinates fed in comprise ten bit positions compared with the eightbit positions of the coordinates which are finally determined by theimage memory. It may then happen that the coordinates (with respect tothe image memory) do not change from one output to the following one. Inorder to prevent faulty evaluation in this situation, provision is madeaccording to another development for relaying of the temporary storageonly to be effected if at least one of the coordinates alters fromtiming cycle to timing cycle.

It is only possible to obtain a provisional derivation of the first pairof coordinates, due to the lack of preceding comparison coordinates. Inthis further development, provision can therefore also be made that forthe first data which are fed in coordinates are stored, independently ofthe logical linkage, which are corrected after the completion of a cyclearound the object at this point.

For the graphical display of information, a rule of precedence isgenerally necessary for the objects or for the planes between theirappearance in the foreground and in the background. With thisdevelopment, this can be ensured by storing coordinates of the contoursof a plurality of objects in the first memory, by determining a rule ofprecedence of planes in which the objects should be displayed with thestorage in the second memory of the data which describe the colour ofthe objects, and by taking the rule of precedence into consideration onreading out the data from the second memory.

Memory components which are conventional in the art are suitable forcarrying out this development of the procedure. In this respect,provision can be made according to one advantageous embodiment forstorage of the coordinates to be effected by storing the coordinates oftwo image elements under an address representing one of the respectivelines.

Depending on the particular requirements, however, another embodimentmay be advantageous which consists of effecting storage of thecoordinates by storing a 1-bit signal in an image memory in the elementgiven by the respective coordinate.

The procedure according to the invention can be employed for displayingone or more objects in one plane and with one colour. However, it isalso possible to display objects in a plurality of planes using theprocedure according to the invention. In this other embodiment, eachplane then merely requires an image memory one bit wide and a memory forthe colour corresponding to the desired colour resolution. Since digitalcomponents are frequently designed for the processing of signals whichare eight bits wide, eight planes can be processed particularlyadvantageously. Practically all applications can therefore be covered.

One advantageous embodiment of this development consists of effectingthe logical linkage according to the following probability table:

    ______________________________________                                        Y2 = Y1 & Y2 < Y3 & Y2 < X1                                                                           non-inverting                                         Y2 = Y1 & Y2 > Y3 & X2 > X1                                                                           non-inverting                                         Y2 < Y1 & Y2 = Y3 & X2 > X3                                                                           non-inverting                                         Y2 > Y1 & Y2 = Y3 & X2 < X3                                                                           non-inverting                                         Y2 < Y3 & Y2 = Y3       non-inverting                                         Y2 > Y3 & Y1 = Y3       non-inverting                                         Y2 = Y1 & Y2 < Y3 & X2 > X1                                                                           inverting                                             Y2 = Y1 & Y2 > Y3 & X2 < X1                                                                           inverting                                             Y2 < Y1 & Y2 = Y3 & X2 < X3                                                                           inverting                                             Y2 > Y1 & Y2 = Y3 & X2 > X3                                                                           inverting                                             Y2 < Y1 & Y2 > Y3       inverting                                             Y2 > Y1 & Y2 < Y3       inverting                                             Y1 = Y2 = Y3 & X2 < X1 & X2 > X3                                                                      setting to "0"                                        Y1 = Y2 = Y3 & X2 > X1 & X2 < X3                                                                      setting to "0"                                        Y1 = Y2 = Y3 & X2 > X1 & X2 > X3                                                                      setting to "1"                                        Y1 = Y2 = Y3 & X2 < X1 & X2 < X3                                                                      setting to "1"                                        ______________________________________                                    

where X1, Y1 denote the following coordinates, X2, Y2 denote the currentcoordinates and X3, Y3 denote the preceding coordinates.

With this embodiment it is ensured, even for very complicated shapes ofobjects, that an even number of 1-bit signals occurs within one line.Complicated shapes of this type are present, for example, when an objecthas a point or constrictions.

Examples of embodiments of the invention are explained in more detail inthe following description and are illustrated in the drawings with theaid of several Figures, where:

FIG. 1 is a block circuit diagram of a device according to theinvention;

FIG. 2 is a more detailed illustration of a memory which is provided inthe device shown in FIG. 1 for generating various data which relate tolines to be displayed;

FIG. 3 shows a detail from the illustration of FIG. 2;

FIG. 4 illustrates a Table which is stored in a memory in thearrangement shown in FIG. 3;

FIG. 5 is a Table for explaining a memory in the device shown in FIG. 1;

FIG. 6 is a detailed illustration of a fader which is provided in thedevice shown in FIG. 1;

FIG. 7 is a block circuit diagram of another arrangement for carryingout the procedure according to the invention;

FIG. 8 illustrates a circuit for the logical linkage of a plurality ofsuccessive coordinates and for deriving the 1-bit signals;

FIG. 9 comprises schematic illustrations showing the derivation of the1-bit signals;

FIG. 10 is a block circuit diagram of a third arrangement for carryingout the procedure according to the invention; and

FIG. 11 is a block circuit diagram of a fourth arrangement for carryingout the procedure according to the invention.

In the Figures, identical components are denoted by identical referencenumerals. The embodiments exemplified and parts thereof are in factillustrated as block circuit diagrams. However, this does not mean thatthe embodiments exemplified are restricted to a design which employsindividual circuits corresponding to the blocks. Rather, thearrangements can be produced in a particularly advantageous manner withthe aid of highly integrated circuits. In this connection, a digitalsignal processor can be used, which with suitable programmingsubstantially performs the functions illustrated in the block circuitdiagrams.

The bit widths of the individual signals which are given below haveproved to be advantageous in a device according to the invention whichwas constructed in practice. Depending on the detailed requirements andon the possibilities of the technology employed in each case, other bitwidths and signal formats may also be selected.

In the device shown in FIG. 1, a graphic processor which is known in theart generates graphic data DL and DA, which relate to lines and areas.In addition, control data DC, which are described later, are generatedby the graphic processor 1. A video read-write memory (video RAM) 2, 3is loaded with the data DL, DA in each case. Video memories of this typeare designed for the storage of defined data for each image and for lineby line read-out. Two memories, which can each be loaded and read outalternately, are frequently provided in video memories. Since videomemories such as these, including their associated control circuits, canbe obtained as component parts, a detailed description of the videomemories 2, 3 is not necessary.

However, one special feature when using the video memory 3 within thescope of the device according to the invention is that one of the bitpositions of the stored data is assigned in each case to atwo-dimensional object which lies in one plane each time. For an objectsuch as this, it is merely the presence for each image element or thespatial extent which is stored--but not the attribute thereof such ascolour or transparency. For the sake of simplicity, colour, transparencyand optionally intensity are also designated below as a property of anarea or a line. Two-dimensional objects can therefore be displayed ineight different planes with the eight-bit wide signals RA which are readout from the video memory 3. A particularly advantageous procedure forgenerating the signals RA for the areas is described in German PatentApplication P 44 46 783.4.

The signals RL and RA for the lines and the areas are each fed to aread-write memory 4, 5. On account of their assignment to the lines andareas, respectively, these memories are denoted as an L-RAM and an A-RAMin the drawing, but for the sake of simplicity are termed memory 4 andmemory 5 in this description.

A line colour LC or an area colour AC and a line factor LF or an areafactor AF are stored under an address in each case in memories 4 and 5,respectively. In addition, memory 4 also contains a line intensity LIfor each address. The contents of the two memories 4, 5 can be loaded bythe graphic processor 1 depending on the requirements; in detail, thiscan be effected for an operating phase as a whole or image by image viaa data bus 6 which carries the control data DC.

The signals RL contain, in binary coded form, the information on whichof the colours stored in memory 4 the respective line object shouldreceive. The signals RL also comprise intensity information which isrequired for the subsequent suppression of foldover distortions.

A diverse variation of the display of two-dimensional objects which aregiven by signals RA is possible due to memory 5. Thus the colour oftwo-dimensional objects which do not overlap other objects can firstlybe determined as desired. In this situation signals RA comprise a 1 inone bit position only. Any desired colour and any desired factor whichare assigned to the respective object can be stored under this addressin the memories.

If objects overlap, any "mixed colour" and any factor can be storedunder each address which then occurs. For example, an address such asthis may have the value 11001000 when objects are situated in planes 1,2 and 5 for the image elements concerned in each case. In thissituation, for example, one of the following colours can be stored inthe memory 5:

the colour of the object in the first plane; this means that the objectin the first plane is not transparent. The further objects are notvisible behind the object in the first plane.

a natural mixed colour which would be produced, for example, when filmsprinted with transparent objects are superimposed and are observed fromthe side of the incident light, so that subtractive colour mixingresults. In this situation, for an overlap of the object in plane 1 withthe colour yellow and of the object in plane 2 with the colour cyan andof the object in plane 5 with a non-transparent white a colour greenwould have to be stored in memory 5 for the aforementioned address, sothat a substantially natural impression would be produced onreproduction.

The "mixed colour" can be determined in departure from calorimetricprinciples, for example as a warning colour when two objects overlap.

For each address, a further factor LF or AF is stored in memories 4, 5,respectively. These factors represent the transparency of the entireobject, the colour of which is determined by signals LC and AC, inrelation to a background signal MAP which is fed in at 7. These factorsare fed via dimmer circuits 8, 9, which are explained below, to twofaders 10, 11. It is thereby ensured in each case that, depending on themagnitude of the factor LF or AF, respectively, only the backgroundsignal MAP, a mixture of the background signal MAP and the respectivecolour LC or AC, or the colour LC or AC, respectively, on its own, isfed to the inputs of a further fader 12 by the faders 10, 11. Thefurther fader 12 receives, as a control signal, the line intensity LIstored in memory 4. Amongst its other uses, the fading between the linecolour and the area colour serves to eliminate foldover distortions.Six-bit wide digital colour value signals R, G, B can each be taken fromthe further fader 12 and fed to a reproduction device 13. The digitalcolour value signals R, G, B can also be converted into signals of othervideo standards.

The dimmer circuits 8, 9, as well as a further dimmer circuit 14,essentially consist of a multiplier which multiplies the line factor LF,the area factor AF and the background signal MAP fed in at 7 by adimming factor in each case, wherein the dimming factors for the linefactor and the area factor are the same in the embodiment illustrated,but can also be different. The dimming factors are written to a dimmingregister 15 by the graphic processor 1, via the bus system 6. Because itis no t the line colour LC or the area colour AC, but instead is thecorresponding factors which are multiplied by the dimming factors, thebrightness of the reproduced image can be controlled without the overallperception of the image being falsified and the recognisability of theindividual objects thereby being reduced.

FIG. 2 is a detailed illustration of memory 4. Eight-bit wide data RL(FIG. 1) from video memory 2 are divided up into five-bit wide data RMCand three-bit wide data RMI. In this connection, C denotes colour and Idenotes intensity. The bit positions RMC which represent colour are fedvia input 21 to the address inputs of four read-write memories 22, 23,24, 25. The bit positions RMI representing the intensity are fed via aninput 26 to address inputs of a further read-write memory 27. Read-writememories 22 to 25 and 27 can be loaded by the graphic processor 1 viathe data bus 6 (FIG. 1) with the properties scheduled for the respectivelines.

The memory arrangement illustrated in FIG. 2 also contains a multiplexercontrol circuit 28, which is controlled by signal RA from video memory 3(FIG. 1) via an input 29. Details of the multiplexer control circuit 28are explained in FIG. 3. For each value of the data RMC fed in at 21, aline colour is stored in memory 22 as a 15-bit wide value and a six-bitwide value is stored in memory 23 as a line factor. In addition, foreach value of RMC the memory 24 contains a bit LT which indicateswhether the respective line is intrinsically to be displayedtransparently. In memory 25, a priority is stored for each value of RMC.This priority determines the rule of precedence with which therespective line is to be displayed between the foreground and thebackground. This four-bit wide signal LP, as well as the one-bit widesignal LT, are fed to the multiplexer control circuit 28. This four-bitwide signal LP, as well as the one-bit wide signal IT, are fed to themultiplexer control circuit 28.

The three-bit wide signal RMI serves to read out the signal LI (lineintensity) from memory 27. The latter signal has a maximum in the middleof the lines and decreases to war ds the edges. Foldover distortions arethen suppressed by the fade-over between line and area or background inthe fader 12.

For various image contents it has proved advantageous to replace theproperties of lines by properties of the areas adjoining the lines. Forthis purpose two multiplexers 30, 31 are provided in the device shown inFIG. 2, to which firstly the output signals of read-write memories 22and 23 and secondly the area colour AC and the area factor AF can be fedfrom memory 5 (FIG. 1) via inputs 32, 33. The multiplexers 30, 31 arecontrolled by the multiplexer control circuit 28. The outputs 34, 35 ofthe multiplexers carry signals LC and LF.

A third multiplexer 36 serves to replace the line intensity LI by thevalue 0; this is also controlled by the multiplexer control circuit 28.Signal LI can be taken off at output 37.

FIG. 3 is block circuit diagram of the multiplexer control circuit 28,to which signals LP and LT from memories 24, 25 are fed at 41 and 42. Inaddition, the multiplexer control circuit 28 receives signal RA fromvideo memory 3 (FIG. 1) via an input 43. Two signals BL and AD arederived from signal RA with the aid of a table stored in a memory 44.The signal TL, which has a width of four bits, indicates the priorityplane in which the object which is situated furthest towards the frontin each case is situated. This signal is compared in a comparator 45with the line priority LP. If the line priority is less than or equal toTL, the output signal LU (=lines underneath) is set to 1.

The further signal AD which is read out from the table 44 assumes thevalue 1 when an object is present in at least one plane. Signals LU andAD are fed, together with the signal LT (=lines transparent), to an ANDgate 46. The output 47 of the AND gate carries a signal SACF whichcontrols the multiplexers 30, 31 (FIG. 2) in such a way that, when thevalue of the signal SACF from the multiplexers 30, 31 is 1, signals ACand AF, and therefore the properties of the area, are fed as signals LCand LF to the outputs 34, 35 (FIG. 2) of the line memory. The conditionwhich is imposed in this respect by means of the AND gate 46 is that anarea must actually be present, that the line is underneath the areawhich is placed furthest towards the front, and that signal IT indicatestransparency.

By means of a further AND gate 48, a signal SOI is derived which istaken off at the output 49 and is fed to the multiplexer 36 (FIG. 2).This signal sets signal LI (line intensity) to zero. It is generated bythe AND operation at 48 (set equal to 1) if an area is actually present,if the respective line is underneath the area situated furthest towardsthe front, and if the area is not transparent. Signal LT is fed to theAND gate 48 via an inverter 50 for the latter.

FIG. 4 shows the table stored in the memory 44, namely the dependency ofsignals TL and AD on signal RA with bit positions (7) to (0) which isfed in. Signal TL denotes the highest priority plane in which an area issituated in each case. For example, if no area is present on the imageelement considered at the time considered, all the bit positions ofsignal RA, and signals TL and AD, are equal to 0. If an area is situatedin the frontmost plane, which is represented by bit position (7) ofsignal RA, signal TL is 1000 and signal AD is 1, for example. It is thenunimportant whether the areas are present in the planes situated furtherbehind; this is represented in the table by an X.

In order to illustrate the function of memory 5 (FIG. 1), FIG. 5 shows aportion of a table which represents the content of the memory. As in thetable shown in FIG. 4, the bit positions of signal RA serve as inputquantities or addresses, so that a total of 256 memory spaces or linesof the Table illustrated in FIG. 5 are stored. For each address, a valueof sign al AC (area colour) and of signal AF (area factor) is stored.The 12 bit positions of signal AC are divided into three colour valuesR, G, B such as red, green and blue.

Memory 5 is designed as a read-write memory to which any data can be fedunder the addresses RA via the data bus 6 (FIG. 1). This can occurduring the vertical frequency blanking-out interval, for example, so that the properties of the objects can vary quasi-continuously. However,it is also possible to reload memory 5 each time if defined types ofoperation are set.

Line a of the table shown in FIG. 5 represents the case of an objectsituated in the frontmost plane, to which the colour red is assigned.There are no objects situated in the other planes. Line b represents thecase of an object in plane 2, whilst line 3 shows an object in the thirdplane, the colour of which comprises proportions of both red and green.In the fourth line d, a portion of which is illustrated, the red objectin the first plane and the object in the third plane overlap, for whicha mixed colour with a higher proportion of red is provided.

A mixed colour such as this allows the object in the front plane in eachcase to appear transparent. If this is not to be the case, the colour ofthe object in the front plane is selected for the overlapping parts ofthe areas, which is illustrated in line e of FIG. 5, for example. Acomparison with line b shows that despite the addition of the 1 in thethird bit position the colour has not changed.

Signal AF is a measure of the transparency of the object as a whole,which object is represented in each case by signal AC. At the maximumvalue 1111 no transparency is present, in lines b and e for example. Theobjects according to lines a, c and d are semi-transparent, however. Allentries in the table can be programmed independently of each other. Forexample, another mixed colour can thus be loaded (R, G, B in line d)without the colours of the object itself being altered.

FIG. 6 is a more detailed illustration of the fader 12 (FIG. 1). A fader51, 52, 53 is provided for each colour value signal R, G, B. The six-bitwide output signals of fader 10 (FIG. 1) are fed to inputs 54, 55, 56.Inputs 57, 58, 59 each contain output signals of fader 11 which are sixbit positions wide. Pairs of these signals which relate to the samecolour are each written with a cycle Clk to one of the faders viaregisters 61 to 66. A further register 60 serves for the temporarystorage and writing-in of the line intensity LI via input 67. Each ofthe faders 51, 52, 53 essentially consists of two multipliers 68, 69, towhich firstly one of the input signals is fed and to which secondly theinverted or non-inverted signal LI is fed. Thus one input signal ismultiplied by LI and the other input signal is multiplied by the unitcomplement of LI each time. The output signals of the multipliers 68, 69are fed to an adder 70, the output 71, 72, 73 of which carries thesignal R, G or B.

In the arrangement shown in FIG. 7 a graphic generator 81 is providedwhich calculates the X, Y coordinates of the points on the contour of anobject to be displayed and outputs them in succession. In addition, dataC are output which are valid for the object as a whole and whichdescribe the colour of the object. In order to display the object bymeans of an image reproduction device 82 which periodically scans a linegrid, an image memory 83 is provided which is hereinafter called acontour memory. The address space of this contour memory reflects thegrid-like structure of the image with Ymax lines and Xmax image elementsper line. The image memory 83 has inputs ADDR for addresses for writingand reading in each case, a data input DI and a data output DO.

In the contour memory 83 a bit can be stored under each address. Inorder to reproduce an object 85, those image elements which form thecontour 84 of the object 85 are set to the value "1" corresponding tothe X,Y coordinates generated by the graphic generator 81, whilst thoseon the image elements have the value "0". Thereafter, the contour memory83 is read line by line, for which purpose x,y addresses are fed in froman address generator 86. A timing circuit 97 takes care of thechronological progress of the individual functions, particularly thewrite and read operations in the contour memory 83.

As will be described more precisely later in connection with FIG. 8, itis ensured that an even number of image elements is set to "1" in eachline. When each line is read out, a signal which has two pulses 89, 90for each line 87 which cuts the object 85 is generated at the output DOof the contour memory 83, as is indicated there. This signal triggers aD flip-flop 91, at the output of which a square pulse is present, thewidth and position of which represent the object in the respective line.During this period, the signal which is stored in a memory 94 (colourmemory) and which represents the colour is fed to the image reproductiondevice 82 by a gate circuit 93. Further signals, which represent linesand characters for example, and which are fed in at 99, can be added tothe signals generated with the procedure according to the invention in acircuit 98.

In order to ensure that only two 1-bit signals occur in each line 87which cuts the object 85, a filter circuit 95 is provided which derivessignals A and B from the X, Y coordinates fed in. These signals are fedto a logic circuit 96 which is connected to an input and an output ofthe contour memory. Reading, modification and re-writing is therebypossible for each image element. This has become known by the termread-modify-write.

If a new object 85 or a new phase of movement of the same object iswritten to the contour memory 83, the content of the contour memory isfirst deleted, namely all image elements are set to "0". The graphicgenerator thereupon commences the output of X, Y coordinates, from whichfirstly the X, Y addresses are derived and secondly signals A and B aregenerated in the filter circuit 95. With the aid of the logic circuit96, these signals can leave the respective image element which isaddressed unchanged, can invert it, set it to "0" (reset) or set it to"1" (set). During these events, the generation of square pulses atoutput 92 of the D flip-flop 91 can be prevented by the data input ofthe D flip-flop 91 being set to "0" by the timing circuit.

In the case of the contour memory, which has not been describedpreviously (all bits=0), and without the risk of obtaining an odd numberof 1-bit signals, the logic circuit 96 inverts the image elementssituated on the contour. This is the situation for a vertical line, forexample. However, a departure from this procedure is necessary, forexample, for lines which are exactly horizontal, only the end points ofwhich may be set to "1" so that the flip-flop 91 remains set during theentire line. Further operations are also necessary for corners, pointsand constrictions of the object, and are described below in connectionwith FIGS. 8 and 9.

FIG. 8 shows the filter circuit 95, to which the X and Y coordinates arefed at 101 and 102 from the graphic generator 1 (FIG. 7). The Xcoordinate is delayed by one timing cycle each time by means of tworegisters 103, 104 supplied with clock pulses, so that three Xcoordinates X1, X2, X3 which are obtained in succession are availablesimultaneously. The Y coordinates Y1, Y2, Y3 are generated in the samemanner by means of registers 105, 106. X1, X2 and X3 are each comparedwith each other in pairs in comparators 107, 108, 109. A correspondingcomparison of the Y components is made by means of comparators 110, 111,112.

Each of the comparators generates output signals which denote threesituations, namely that the signals at its inputs are equal, or that thefirst signal or the second signal is greater than the other signal ineach case. These output signals are fed to a logic circuit 113 whichforms statements for the derivation of the 1-bit signals correspondingto the probability table presented above--starting from a contourmemory, the content of which is set to "0". Signals A and B are therebygenerated, which are coded as follows, for example:

    ______________________________________                                        statement           A     B                                                   ______________________________________                                        non-inverting (NI)  0     0                                                   inverting (I)       1     0                                                   set (S)             1     1                                                   reset (R)           0     1                                                   ______________________________________                                    

Signals A and B are delayed by one timing cycle by means of a register114 and are fed via an output 115 to the logic circuit 96 (FIG. 7). Theassociated X, Y coordinates can be taken off at further outputs 116,117. Due to the delay by means of register 114, the signals at output115 are in the chronological plane of the coordinates X2, Y2. Inrelation to an image element with these coordinates, the coordinates X1,Y1 constitute the preceding image element and the coordinates X3, Y3constitute the following image element in each case.

On the evaluation by the filter 95 (FIG. 7) of the preceding coordinatesand of the future coordinates to be fed in, various possibilities arisedepending on the course of the contour in detail 64. This number ofpossibilities arises in that during the progressive formation, imageelement by image element, of the 1-bit signals, eight adjacent precedingimage elements and eight future adjacent image elements in anycombination have to be acquired in addition to the image pointconsidered in each case.

These 64 cases are schematically illustrated in FIGS. 9a and 9b, and arecombined to form groups of cases for which the same condition is validor for which the same output signals of the comparators (FIG. 8) arepresent in each case. The illustrations are based on a clockwise cyclearound the object. The future, the present and the preceding imageelement is denoted in each case by italic FIGS. 1, 2, 3.

The cases of group G1 relate to internal corners at the right-hand edgeof the object. The object area is therefore situated to the left of orbelow the image elements illustrated. The image element which issituated in the corner in each case is not inverted, i.e. a 1-bit signalis not stored for these coordinates. It is to be assumed that a 1-bitsignal is already present or is still being generated in the same lineat the left-hand edge of the object. However, the 1-bit signal whichstill remains for denoting the right-hand edge cannot be situated atthis internal corner, since the contour is still progressing to theright.

The cases of group G2 each represent a corner situated at the bottomright, for which a 1-bit signal must be set. The same applies to theexternal corner situated at the top left according to group G3. GroupsG4 and G5 again relate to internal corners, namely on the left side ofthe object. A 1-bit signal is not generated at these corners, i.e. thezeros which were previously written to the memory are not inverted.Groups G6 and G7 again relate to external corners, namely to those atthe left-hand and right-hand edge of the object, so that an inversion ofthe image element is effected. The cases of group G8 are again internalcorners, where no inversion is effected.

In group G9, all the cases are combined in which the linked coordinatesare in ascending order, whilst in the cases of group G10 the linkedcoordinates are processed descending at the right hand edge of theobject. In all cases only one image element which is inverted occurs foreach line.

The cases of groups G11 and G12 are characterised in that the verticalcomponent of the direction of processing is reversed at the presentimage element. This image element would result in an odd-numberedquality in the respective line and is therefore not inverted.

The cases of groups G13 and G14 are parts of sections of the contourwhich run in the direction of the lines, where no 1-bit signals are tobe set for the image elements situated inside the end points. Thepresent image element is therefore reset in both cases.

The cases of groups G15 and G16 relate to end points of a horizontallyextending line or point of an object, at which the direction ofprocessing is reversed. It is therefore necessary to set a 1-bit signal.

With the arrangement shown in FIG. 7 it is possible to display an object85 using the image reproduction device 82. In many specificapplications, however, a plurality of objects has to be displayedsimultaneously. In the arrangement shown in FIG. 10 a contour memory 121is provided for this purpose, in which each item of informationcomprising a plurality of bits can be stored under an address. Comparedwith contour memory 83 (FIG. 7), contour memory 121 has a plurality ofplanes. Since eight-bit words (bytes) are frequently used in digitaltechnology, memories with eight planes are easily produced orobtainable. Thus the contours of eight different objects can be storedin contour memory 121, and the colours of these objects can be stored inan eight-fold colour memory 122.

More or less than eight planes can also be provided, however, accordingto the requirements in the particular case. For the sake of clarity,only three planes are indicated in FIG. 10. A logic circuit 123 andflip-flops 124 are of multiple design corresponding to the number ofplanes. A single arrow pointing towards the middle plane means thatsignals are fed to all planes. If different signals are intended for theindividual planes, a plurality of arrows which point towards differentplanes is illustrated.

The contours of the individual objects are written to the contour memory121 sequentially, for which purpose, during a period in which the X, Ycoordinates and the colour C for a first object are output, the logiccircuit 123 is controlled by the graphic generator in such a way that amodification of the 1-bit signals in the read-modify-write cycle is onlyeffected in that bit of a byte which is read out from contour memory 121under the address corresponding to the coordinates, which bit belongs tothe plane of the respective object. If the contour of an object iswritten to the associated plane of memory 121, the data output for thesecond object is effected by the graphic generator 81, whereupon onlythe bits belonging to the second object are then processed in the logiccircuit 123.

Read-out of the contours is effected in such a way that the entire byteis read out under an x, y address in each case and is distributed to theinputs of flip-flop 124. Square signals are then available line by lineat the outputs of flip-flop 124, corresponding to the position and widthof the object on the respective line.

These signals are fed to a priority circuit 125 in which the signals aretransmitted or suppressed in accordance with an established priority.For example, as long as the signal with the highest priority has thelevel "1", which is the situation inside the area of the object, allother signals are set to level "0" irrespective of their input value. Adisplay of the individual objects in a plurality of planes between theobserver and the background is thereby possible. When there areoverlaps, the front object in each case covers the one behind. Suitablepriority circuits, which essentially consist of logic elements, areobtainable commercially, so that a detailed description of prioritycircuit 125 is unnecessary.

A multiplexer 126 is controlled by the output signals of prioritycircuit 125 in such a way that signals at one of its inputs I1, I2, I3are each transmitted to output O. Inputs I1, I2, I3 of the multiplexereach contain signals from a plane of the colour memory 122. In thearrangement shown in FIG. 7, output O of multiplexer 126 is connected tothe image reproduction device 82 via a circuit 98.

In the arrangement illustrated in FIG. 11 the contour memory 131 is ofdifferent construction to the contour memories 83, 121 in thearrangements shown in FIGS. 7 and 10. For the storage of one of theimage elements forming the contour, a 1-bit signal is not stored underthe address corresponding to the coordinates, but instead the Xcoordinates of two image elements which form the contour and which aresituated on a line are each stored under a Y address which denotes thisline. This is again effected for the contours of a plurality of objects,with regard to which three planes are illustrated in FIG. 11 butrepresent an arbitrary number of planes.

The object to which the X coordinates which are fed to the memory ineach case belong is again communicated by the graphic generator 81 asquantity Z. This is fed, together with Y, to an address input ADDR ofcontour memory 131, so that the address under which the two Xcoordinates are stored comprises the information: line Y, plane Z. Sothat only two image elements in each line are marked as belonging to thecontour, a filter 95 is likewise provided in the arrangement shown inFIG. 11. The X coordinates leaving this filter are processed with theaid of signals I and S in a logic circuit 132, in a similar manner tothe 1-bit signals in the embodiments illustrated in FIGS. 7 and 10.Depending on its relationship to the cases illustrated in FIG. 9, an Xcoordinate is either re-written, deleted or over-written by another.

In order to read out the signals describing the contours from contourmemory 131, the x, y coordinates are generated by the address generator85, as for the other embodiments exemplified, in such a way that duringa line y the addresses or x coordinates of all the image elements in aline are generated in succession. Contour memory 131 is constructed insuch a way that when it is read the data stored under the respectiveaddress part y in all planes Z are read out simultaneously. The dataread out from each plane are each compared with x in a comparator 133,134, 135. If the value x reaches one of the X coordinates which arestored for one line and one plane in each case, equality is determinedin the respective comparator 13, 134, 135 and a pulse is emitted for theduration of this timing cycle. These pulses are then processed furtheras described with reference to FIGS. 7 and 10 in connection with theother embodiments exemplified.

We claim:
 1. A method for displaying objects using an image reproductiondevice with a raster of scanlines, comprising the steps of:(a) inputtingdata from a graphic processor which contain coordinates of successivepoints of contours (border lines) of the objects; (b) deriving from thecoordinates of the points an even number of contour image elements perscanline, including the case of overlapping objects; (c) storing thecontour image elements in at least one memory by setting data ataddresses which correspond to locations of the contour image elements topredetermined values; (d) inputting and storing in at least one furthermemory further data which describe colors, there being one colorassigned to each object, each of which colors extends over the entireobject; (e) reading out the data of the contour image elements scanlineby scanline from the at least one memory; (f) changing the read out databy setting the data of image elements between two contour image elementsto said predetermined values; (g) supplying the changed data asaddresses to the at least one further memory; and (h) reading out thefurther data under the addresses from the at least one further memory asdigital video signals which are fed to the image reproduction device. 2.The method according to claim 1, wherein the digital video signals aremixed with further digital video signals which are fed in.
 3. The methodaccording to claim 1, wherein data which describe the shape and positionof line objects are stored in a first image memory and data whichdescribe the shape and position of two-dimensional objects are stored ina second image memory, and wherein the data read out from the first andsecond image memories are fed as addresses to a first and a secondfurther memory in each case.
 4. The method according to claim 3, whereinthe data which describe the shape and position comprise a plurality ofbit positions for each image element and each bit position is assignedto a display plane, particularly to an object to be displayed in thisdisplay plane.
 5. The method according to claim 4, wherein the datawhich describe the shape and position comprise a plurality of bitpositions for each image element, wherein a bit position is assigned toeach display plane, particularly to an object to be displayed in thisdisplay plane, wherein signals which can be taken from the first furthermemory and which indicate the plane of the respective line object arecompared with the data read out from the second image memory, andwherein the digital video signals representing the lines are replaced bydigital video signals which represent objects for those image elementsfor which the comparison shows that a line runs behind an object.
 6. Themethod according to claim 1, wherein the transparency of the objects isadditionally stored in the at least one further memory.
 7. The methodaccording to claim 3, wherein digital video signals which relate to theline objects and digital video signals which represent the color of thetwo-dimensional objects are each mixed with a background signal using atransparency factor, and that the mixed products are mixed with eachother using a further factor which describes the line intensity.
 8. Themethod according to claim 7, wherein the factor which describes the lineintensity falls off gradually from the middles of the lines to theiredges in order to avoid foldover distortions.
 9. The method according toclaim 1, wherein the color and transparency of an object or of acombination of a plurality of overlapping objects are stored in the atleast one further memory under an address in each case.
 10. The methodaccording to claim 1, wherein the further data for each address can beindependently fed in and stored in the further memories.
 11. A methodfor displaying objects using an image reproduction device with a rasterof scanlines, comprising the steps of:(a) inputting data from a graphicprocessor which contain coordinates of successive points of contours(border lines) of the objects; (b) deriving from the coordinates of thepoints an even number of contour image elements per scanline whether ornot an object is hidden by another, overlapping object; (c) storing thecontour image elements in at least one memory by storing addresses whichcorrespond to locations of the contour image elements; (d) inputting andstoring in at least one further memory further data which describecolors, there being one color assigned to each object, each of whichcolors extends over the entire object; (e) comparing inputted addresseswhich are incremented according to the raster of scanlines to the storedaddresses resulting in data which are set to a predetermined level whenthe incremented addresses correspond to the addresses of the contourimage elements or the image elements between two of the contour imageelements in the same scanline; (f) supplying the resulting data asaddresses to the at least one further memory; and (g) reading out thefurther data under the addresses from the at least one further memory asdigital video signals which are fed to the image reproduction device.12. The method according to claim 11, wherein the coordinates arederived in such a way that the number of image elements forming thecontour of each object is even within each line.
 13. The methodaccording to claim 12, wherein sections of the contour which do not runin the direction of the lines are formed from image elements at theirend points and from one image element for each cut line, that sectionsof the contour which run in the direction of the lines are formed fromimage elements at those ends which are situated at external corners ofthe object, and that individual image elements which are situated at thepoint of intersection of two sections of the contour which do not run inthe direction of the lines and which form a corner of the object are notwritten to the image memory.
 14. The method according to claim 13,wherein for the successive derivation of the coordinates, the fed-indata which contain the contour are fed in, that the (X, Y) coordinatesare temporarily stored for three successive timing cycles, that twosuccessive coordinates and two coordinates which are delayed by twotiming cycles in relation to each other are compared in each case, andthat instructions for the modification, non-modification or setting ofcoordinates previously stored in the first memory are produced by alogical linkage of the comparison results.
 15. The method according toclaim 14, wherein relaying of the temporary storage is only effected ifat least one of the coordinates alters from timing cycle to timingcycle.
 16. The method according to claim 14, wherein for the first datawhich are fed in coordinates are stored, independently of the logicallinkage, which are corrected after the completion of a cycle around theobject at this point.
 17. The method according to claim 11, whereincoordinates of the contours of a plurality of objects are stored in theimage memory, wherein, with the storage in the further memory of thedata which describe the color of the objects, a rule of precedence ofplanes in which the objects should be displayed is determined, andwherein the rule of precedence is taken into consideration on readingout the data from the further memory.
 18. The method according to claim11, wherein storage of the coordinates is effected by storing thecoordinates of two image elements under an address representing one ofthe respective lines.
 19. The method according to claim 11, whereinstorage of the coordinates is effected by storing a 1-bit signal in theimage memory in the element given by the respective coordinate.
 20. Themethod according to claim 19, wherein the logical linkage is effectedaccording to the following Boolean operation table:

    ______________________________________                                        Y2 = Y1 & Y2 < Y3 & Y2 < X1                                                                          non-inverting                                          Y2 = Y1 & Y2 > Y3 & X2 > X1                                                                          non-inverting                                          Y2 < Y1 & Y2 = Y3 & X2 > X3                                                                          non-inverting                                          Y2 > Y1 & Y2 = Y3 & X2 < X3                                                                          non-inverting                                          Y2 < Y3 & Y2 = Y3      non-inverting                                          Y2 > Y3 & Y1 = Y3      non-inverting                                          Y2 = Y1 & Y2 < Y3 & X2 > X1                                                                          inverting                                              Y2 = Y1 & Y2 > Y3 & X2 < X1                                                                          inverting                                              Y2 < Y1 & Y2 = Y3 & X2 < X3                                                                          inverting                                              Y2 > Y1 & Y2 = Y3 & X2 > X3                                                                          inverting                                              Y2 < Y1 & Y2 > Y3      inverting                                              Y2 > Y1 & Y2 < Y3      inverting                                              ______________________________________                                    